<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>
<body>
    <button>11</button>
    <ul>
        <li>
1
        </li>
    </ul>
    <script>
   var ul  = document.querySelector('ul');
   var btn  = document.querySelector('button');
   var li  = document.createElement('li')
   var lili  = document.createElement('li')
   li.innerText = '123'
   ul.appendChild(li)
   ul.insertBefore(lili,ul.children[0])
       btn.onclick = function(){

    //    var lili =  ul.children[0].cloneNode();
       var lili =  ul.children[1].cloneNode(true);
    //    无参数为浅拷贝
       ul.appendChild(lili);
       }
    </script>
</body>
</html>